JPS6229526B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing conductive composite fibers. (Prior art) Composite fibers in which a conductive layer made of a polymer mixed with conductive particles such as metal particles, carbon black, etc. and a non-conductive layer made of a fiber-forming polymer are well known, and can be mixed with other fibers. It is used for purposes such as imparting antistatic properties. Examples of composite fibers containing carbon black include JP-A-52-107350 and JP-A-55-6540.
The fibers are produced by spinning an antistatic synthetic polymer composition containing 3 to 20% by weight of titanium oxide whose surface is coated with tin oxide as metal particles. was published in 1973.
It is described in Publication No. 92854. (Problems to be Solved by the Invention) However, fibers mixed with carbon black have the disadvantage that they are colored black or gray, and furthermore, if carbon black is mixed in a large amount (enough to impart conductivity) to the spinning material, Not only does it exhibit structural viscosity and fluidity is significantly reduced, but also carbon black is deposited inside the spinning device, making it difficult to spin the yarn stably for a long period of time. On the other hand, it is very difficult to produce metal particles with a particle size of 1 μm or less, especially 0.5 μm or less, and ultrafine particles are extremely expensive and have little practical use. Furthermore, the smaller the particle size of metal particles, the more likely they are to fuse together (sinter) and become coarse or precipitate as metal lumps due to high temperature and high pressure during melt-kneading and melt-spinning.
Even if the amount is approximately 20% by weight, it is extremely difficult to melt-spun a mixture containing a larger amount. Moreover, in the case of metal particles, unlike carbon black, if the content is about 3 to 20% by weight, the desired conductive effect cannot be obtained. An object of the present invention is to provide a conductive composite fiber that is less colored and has excellent conductivity. Another object is to provide a method for manufacturing such conductive composite fibers industrially easily and at low cost. (Means for Solving the Problems) The object of the present invention is to provide a non-conductive layer component made of a fiber-forming polymer, and at least
50~15% by weight of thermoplastic polymer with melting point lower than 30℃ and titanium oxide particles with conductive coating below 50
After composite spinning, a conductive layer component consisting of ~85% by weight is heated to a temperature higher than the melting point of the thermoplastic polymer and lower than the melting point of the fiber-forming polymer, and then cooled to form a conductive layer in the conductive layer. This is achieved by a method for producing conductive composite fibers characterized by growing a conductive composite fiber. {The conductive film contains 50% by weight or more of metal oxide and
It is formed from 50% by weight or less of a metal and/or a metal oxide different from the metal oxide. } In the present invention, titanium oxide having a conductive film is used as the conductive particles. Metal films are also available as conductive films, but metal films have the drawback of being unstable and susceptible to deterioration and modification due to oxidation and the like. Some metal oxides are stable and conductive, such as copper oxide, silver oxide, zinc oxide, cadmium oxide,
Examples include tin oxide, lead oxide, and manganese oxide. In particular, by using these metal oxides as the main component (50% or more, especially 75% or more) and adding a small amount (50% or less) of the second component, the conductivity can be significantly increased (for example, about 10 ³ Ω・cm). (below) can be done. Examples of the second component include oxides of different metals and/or the same or different metals.
For example, copper oxide/copper, zinc oxide/aluminum oxide, tin oxide/antimony oxide, zinc oxide/zinc/
Aluminum oxide/aluminum, tin oxide/tin/
Antimony oxide/antimony and those containing partially reduced oxides of antimony and the like are suitable. The method and amount of mixing of the second component (conductivity improving component) are various, but are not limited to those described above as long as they are effective and stable for improving conductivity. Titanium oxide with a conductive metal oxide film is
Specific resistance in powder form is approximately 10 ⁴ Ω・cm (order)
Below, it is particularly preferable to be about 10 ² Ω・cm or less, and 10 ¹
The most preferable value is approximately Ω·cm or less. Actually 10 ² Ω・
cm to ^{10 -2} Ω·cm have been obtained, and can be suitably applied to the purpose of the present invention. (Those with even better conductivity are even more preferred). The specific resistance of the powder is determined by placing a sample of 10 gr in a cylinder with a diameter of 1 cm.
Measurement is performed by applying a pressure of 200 kg from the top of the packing using a piston and applying direct current (0.1 to 1000 V). It is desirable that the conductive particles have a small particle size from the viewpoint of spinnability and conductivity. For example, the average particle size is 1 μm
Below, especially 0.7μm or less, most preferably 0.5~
0.01 μm is used. Generally, the smaller the particle size, the better the conductivity of the mixture when mixed with a polymer. Particles with a particle size of 1 μm or more are not impossible to use, but their performance is significantly inferior. Usually, titanium oxide with a particle size of 0.2 μm or less is commercially produced as a white pigment, and by adding a conductive film to this, a particle size of about 0.3 μm or less can be obtained.
The conductive film can be formed, for example, by vacuum evaporation, by depositing a metal compound (for example, an organic acid salt), baking it to form an oxide, or by partially reducing it. The conductive film preferably has sufficient conductivity and has little coloration, and is preferably one containing zinc oxide or tin oxide as a main component.Among these, a film containing zinc oxide as a main component is most preferable because it has little coloration. Any known thermoplastic polymer can be used as the polymer to be mixed with the conductive particles to form the conductive layer. Examples include polyamide, polyester, polyolefin, polyvinyl, polyether, polycarbonate, and many others. Although fiber-forming polymers are preferable from the viewpoint of spinnability, for the purpose of the present invention, polymers with poor spinnability may also be used (as long as composite spinning is possible).
In particular, from the standpoint of conductivity, materials with a high degree of crystallinity,
For example, crystallinity of 40% or more, especially 50% or more,
Most preferably, it is 60% or more. According to the findings of the present inventors, when mixing with low crystallinity (including non-crystalline) polymers, the mixing ratio (weight ratio) of conductive particles is extremely high, for example, 80
Sufficient conductivity is often not obtained unless the amount is ~95% (by weight). On the other hand, when mixing with highly crystalline polymers, the mixing ratio is relatively small, e.g.
Sufficient conductivity is often obtained at about 50 to 80%, especially about 55 to 75%. Needless to say, the higher the mixing ratio of conductive particles, the lower the fluidity of the mixture and the difficulty of spinning, and the lower the drawability and the strength and elongation of the obtained fibers. The lower the better. That is, a polymer with high crystallinity is preferred. It is unclear why products using highly crystalline polymers have superior conductivity; however, when melted, the particles are uniformly dispersed in the polymer, but upon cooling, solidification, or stretching, the polymer crystallizes. It is assumed that this is because particles are excluded from the crystal part, concentrated between the crystals, and come close to or in contact with each other to form a conductive structure. For example, conductive titanium oxide powder (specific resistance 12Ω cm) 75%, crystalline paraffin
A mixture consisting of 25% exhibits high resistance (specific resistance of 10 ⁸ Ω cm or more) close to that of an insulator when melted (the same applies to liquid paraffin), but when cooled and solidified (crystallized), it exhibits excellent conductivity (specific resistance). 10 ² to 10 ⁴ Ω・cm). (On the other hand, in the case of carbon black,
Excellent conductivity can be obtained even with amorphous polymers,
Conversely, highly crystalline polymers often have poor conductivity because the crystals break the chain of particles. ) As mentioned above, a structure in which the conductive particles are in contact with each other or are very close to each other is preferred in order to obtain high conductivity. However, such a structure may be destroyed or cut during the process of drawing the spun fibers. (On the other hand, stretching may cause the particles to align and grow a conductive structure.) One way to prevent the destruction of the conductive structure due to stretching is to make part or all of the polymer forming the conductive layer non-conductive. In this method, a crystalline polymer having a melting point lower than that of the layer polymer is used, and stretching is performed in a temperature range between that of the non-conductive layer polymer and the low melting point polymer. In this method, the low melting point polymer is molten during stretching, and is then cooled and solidified (crystallized) to grow the conductive structure. For example, a polymer with a melting point of 150°C or higher is used as the non-conductive layer polymer, and a polymer with a melting point of 30°C or higher (preferably 50°C or higher) than that of the non-conductive layer polymer is used as the conductive layer polymer.
C. or higher, most preferably 80.degree. C. or higher), and can be composited and stretched at a temperature between the melting points of both polymers, such as 50 to 260C, particularly 80 to 200C. The second method is to regrow the conductive structure destroyed by stretching by heating and cooling. For example, if the drawn yarn is above the melting point of the low melting point polymer,
The conductive structure can be regrown by heating under tension or relaxation to a temperature below the melting point of the non-conductive layer polymer, followed by cooling. In this case as well, the melting points of both polymers are within the above range, and the difference therebetween is 30°C or more, preferably 50°C or more. Since the polymer must be solidified (crystallized) at the temperature at which the fiber is used, the melting point of a low melting point polymer is 40
℃ or higher, preferably 80℃ or higher, most preferably
It is desirable that the temperature is 100°C or higher, that is, the heat treatment temperature is preferably 50 to 260°C, particularly 80 to 240°C.
Generally, undrawn yarn is heated at too high a temperature (150℃ or higher, especially
Since it is often difficult to stretch at a temperature of 200° C. or higher, the second method has a wider range of applications than the first method. The mixing ratio of conductive particles in the conductive layer varies depending on the conductivity, purity, structure, particle size, chain-forming ability of the particles, the nature and type of the polymer to be mixed, the degree of crystallinity, etc. 85% by weight, preferably 60
~80% by weight. (If it exceeds 80% by weight, the fluidity is insufficient, so it is often necessary to use a fluidity improver.) In addition to conductive titanium particles, it is also used to improve particle dispersibility, conductivity, and spinnability Different types of conductive particles can be used together.For example, metal oxides such as tin oxide, zinc oxide, zirconium oxide, indium oxide, iron oxide, bismuth oxide (preferably those with little coloring and high conductivity), copper, Silver, nickel, iron, aluminum and other metal particles can be used in combination.If used in combination, the mixing ratio of conductive titanium oxide may be lower than the above range, but the main component of the conductive particles (more than 50%) is conductive titanium oxide.In any case,
The specific resistance of the conductive layer of the composite fiber must be approximately 10 ⁶ Ω·cm or less, particularly preferably 10 ⁴ Ω·cm or less, and most preferably 10 ² Ω·cm or less. The conductive layer further contains a dispersant (e.g. wax,
It is possible to add polyalkylene oxides (various surfactants, organic electrolytes, etc.), colorants, pigments, stabilizers (antioxidants, ultraviolet absorbers, etc.), fluidity improvers, and other additives. As the fiber-forming polymer forming the non-conductive layer (protective layer) of the composite fiber, any material that can be melt-spun can be used. For example, nylon 6, nylon
Polyamides such as 66, nylon 12, and nylon 610, polyesters such as polyethylene terephthalate, polyethylene oxybenzoate, and polybutylene terephthalate, polyolefins such as polypropylene and polyethylene, polyvinyl chloride,
Polyvinyl polymers such as polyvinylidene chloride, and copolymers and modified products of these polymers are used. Additives such as pigments, colorants, stabilizers, antistatic agents (polyalkylene oxides, various surfactants, etc.) can be added to the fiber-forming polymer. Composite (joining) of conductive and non-conductive components
can be in any format. Figures 1 to 8 show typical composite types (shaded areas indicate conductive layers). Figure 1 is a core/sheath type (the sheath is also a conductive layer type), and Figure 2 is a side-by-side type. Type, 3rd
The figure shows an example of a three-layer type, FIG. 4 a radial type, FIG. 5 a multiple side-by-side type, FIG. 6 a multi-core type, FIG. 7 a multi-layer type, and FIG. 8 an example of a non-circular core type. Of course, any combination other than the above is possible, and the outline of the fibers may be circular or non-circular. The area ratio occupied by the conductive layer in the cross section of the composite fiber, that is, the composite ratio is arbitrary. This is because there is almost no need to consider the whiteness of the fibers. However, in general, a conductive layer mixed with a large amount of conductive particles tends to be inferior in strength, elongation, etc., so the composite ratio is often preferably about 3 to 80%, particularly about 5 to 60%. The present invention can easily produce white or nearly white fibers, and is suitable for producing white or light-colored fiber products for which carbon black conductive fibers are unsuitable. The fibers of the present invention are in the form of continuous filaments or staples and can be mixed with other chargeable fibers to impart antistatic properties to textile products. The mixing rate is usually about 0.1 to 10% by weight, but depending on the purpose, a mixing rate of 10 to 100% by weight or 0.1% by weight or less may be applied. The mixing may be carried out by blending, doubling, twisting, blending, weaving, knitting, or any other known method. The present invention will be explained below with reference to Examples. Parts and percentages indicate weight ratios unless otherwise specified. Example 1 A zinc oxide film (approximately 15% by weight) was formed on titanium oxide with an average particle size of 0.05 μm, and 4% aluminum oxide fine particles (particle size 0.02 μm) were mixed and fired to produce conductive particles A. Got ₁ . Powder _A1 has an average particle size of 0.06 μm, a specific resistance of 12 Ω·cm, and is almost white (slightly gray-blue). Polymer _P1 is a low-density polyethylene with a molecular weight of about 50000, a melting point of 102°C, and a crystallinity of 37%. Molecular weight approx.
48000, melting point 130℃, crystallinity 77% high density polyethylene is used as polymer _P2 . Polyethylene oxide having a molecular weight of about 63,000, a crystallinity of about 55%, and a melting point of 55°C is used as polymer _P3 . 75 parts of ethylene oxide component/propylene oxide component
A random copolymer with a molecular weight of approximately 20,000 consisting of 25 parts
90 parts of bishydroxyterephthalate and 10 parts of bishydroxyterephthalate were mixed at 245°C using antimony trioxide (600ppm) as a catalyst.
A high viscosity liquid (crystallinity 0%) at room temperature obtained by polymerization under reduced pressure (0.5 Torr) for 6 hours at
75000 polyetherester as polymer _P4 . Polymer P5 is nylon ₆ with a molecular weight of about 16,000, a melting point of 215°C, and a crystallinity of 45%. A mixed polymer obtained by kneading powder A ₁ with polymers P ₁ to _{P 4} at a mixing ratio of 60% and 75%, respectively, was used for the core, and a mixture of polymer P ₅ and titanium oxide at 1% was used for the sheath. The structure shown in the figure is compounded at a compounding ratio of 1/10 (cross-sectional area ratio), spun at 270℃ from an orifice with a diameter of 0.3mm, cooled and oiled, wound at a speed of 1000m/min, and placed on a pin at 80℃. The drawn yarns Y ₁ to _{Y 8} of 20 denier/3 filaments were drawn by 3.1 times. Table 1 shows the core polymer and conductive particle mixing ratio of each fiber and the electrical resistance per 1 cm of single yarn length.

【table】

[Table] Yarns Y ₁ to _{Y 8} are each drawn nylon 6 yarn (2600d/
144f) and crimping, and the combined yarn is
A tufted carpet (loop) was manufactured by using one thread for one course and using nylon 6-wrap crimped yarn (2600d/144f) for the other three courses. The electrostatic potential of the human body when walking on the resulting carpet with leather shoes (25°C, 20% RH) was as shown in Table 2. For comparison, the voltage charged on the human body when walking on a carpet made of only 6-wrap nylon crimped yarn is also shown.

[Table] The yarns Y ₁ to Y ₈ were heat-treated by relaxing them by 3% at 150° C. and are designated as HY ₁ to HY ₈ , respectively. As shown in Table 3, the electrical resistance of HY ₁ to HY ₆ decreased, indicating a considerable improvement in conductivity, but HY ₇ and HY 6 showed a significant improvement in conductivity.
No effect was observed in HY ₈ .

【table】

[Table] Conductive powder obtained by mixing and firing 5% antimony oxide particles (particle size 0.02 μm) on titanium oxide particles with an average particle size of 0.04 μm on which a tin oxide film (approximately 12% by weight) is formed. Let be A ₂ . Powder A ₂ had an average particle size of 0.05 μm, a specific resistance of 9 Ω·cm, and was almost white (slightly gray-blue). The conductive layer was made by mixing 75% of powder A ₂ using polymer P ₂ from Example 1, and the protective layer was made by mixing 2% of titanium oxide with polymer P ₅ . 1/8) and the following is the yarn of Example 1.
Yarns Y ₉ and HY ₉ were obtained in substantially the same manner as Y ₄ and HY ₄ , respectively. The electrical resistance of yarn Y ₉ and HY ₉ is 7.6×10 ⁹ and 1.1×, respectively.
It was ₁₀₉ Ω/cm. Although the conductive layer of HY ₉ was exposed on the fiber surface, the heat treatment was for a short time and there was no yarn breakage or increase in fuzz. Example 3 Consisting of particles A ₁ of Example 1 and polymer P ₂ ,
The core is a mixture of particles with a mixing ratio of 70%, and the molecular weight is approx.
18000 polyethylene terephthalate was used as a sheath and composited at a composite ratio of 1/9 into a cross section as shown in Figure 8.
Spun from an orifice with a diameter of 0.25 mm at 278°C, oiled, wound at a speed of 1500 m/min, and heated at 80°C.
Stretched 3.15 times and further heat treated at 180℃ under tension to create 30 denier/6 filament yarns Y ₁₀ and HY ₁₀
I got it. The electric resistance of single yarn Y ₁₀ and HY ₁₀ is 8.6× respectively.
10 ¹⁰ , 9.5×10 ⁹ Ω/cm. Composite fibers with a conductive part in the core have dielectric breakdown in the sheath when a charged object is nearby and the charge is removed by corona discharge, but as shown in Figure 8, if the core has one or more When the shape has a pointed tip, the above-mentioned dielectric breakdown occurs easily and the antistatic property is excellent. In order to form such a tip, it is preferable that the conductive particles have a smaller particle size, and those having a particle size of 0.1 μm or less are most preferable. Even if the conductive layer is exposed on the fiber surface, for example, those with pointed ends as shown in Figures 3 and 4 are more likely to cause corona discharge and have excellent antistatic properties, so the same method can be used for these as well. It is desirable that the particle size is small. (Effects of the Invention) The fibers obtained by the method of the present invention not only have excellent conductivity, but unlike those using conventional carbon black, they are less colored and can be easily produced industrially. can. Furthermore, the conductive fibers obtained by the method of the present invention can be used in combination with non-conductive fibers and are useful for work clothing, especially dust-free clothing used in the electronics industry.

[Brief explanation of the drawing]

FIGS. 1 to 8 show specific examples of cross sections of the composite fibers of the present invention, and the shaded areas in the figures indicate conductive layers.

Claims (1)

[Claims] 1. A non-conductive layer component made of a fiber-forming polymer;
After composite spinning a conductive layer component consisting of 50 to 15% by weight of a thermoplastic polymer having a melting point at least 30°C lower than the fiber-forming polymer and 50 to 85% by weight of titanium oxide particles having a conductive film as described below. , a conductive composite fiber characterized in that it is heated to a temperature higher than the melting point of the thermoplastic polymer and lower than the melting point of the fiber-forming polymer, and then cooled to grow a conductive structure in the conductive layer. Production method. {The conductive film is formed of 50% by weight or more of a metal oxide and 50% by weight or less of a metal and/or a metal oxide different from the metal oxide. } 2 Claim 1, in which the conductive film of titanium oxide contains zinc oxide or tin oxide as a main component.
The method described in section. 3. The method according to claim 1, wherein the fiber-forming polymer is polyamide, polyester, polyether, vinyl polymer or polyolefin.